This artifact was found in shallow water on a reef together with other artifacts such as plates and pots. Location is along one of the traditional ancient Chinese shipping routes in Southeast Asia. Could this be a Chinese Silver Ingot?
I really don't know. It's not a Sycee and it appears to have no marks on either side. Search up and test it with different techniques to see if it would be silver. The traditional Chinese silver ingots usually have marks on them. Your's may be a older one so one thing you can also do is look very very closely on the surface of the ingot and see if you can find maybe just a tiny almost wiped out mark that could be some sort off numeral of ancient Chinese alphabetic letter mark.